Characterization of mild or asymptomatic patient admitted with Omicron variant of COVID-19 infection in Tibetan mobile cabin hospital China, August-October 2022.

Background: Prior to August 7, 2022, there had been no positive cases of novel coronavirus in Tibet for 920 consecutive days. However, with the first case of Omicron variant infection, the disease rapidly spread and was prevalent in Tibet for nearly 3 months, from August 7th to November 1st. With the spread of the epidemic, the local government responded quickly and established several mobile cabin hospitals to treat patients with mild and asymptomatic Omicron infection. However, the epidemiological and clinical characteristics of these patients are unknown. Methods: This is a retrospective study including a total of 14,264 mild and asymptomatic cases with Omicron infection in Tibet between August to October, 2022. The clinical data and epidemiological characteristics of COVID-19 cases admitted to Tibet mobile cabin hospitals were collected by using standardized forms from mobile cabin hospital database system, including demographic characteristics, onset symptoms, medication use, past medical history, hospitalization time, and discharge time. In terms of statistical analysis, multivariate Cox regression model was used to analyze the relationship between case characteristics and the length of stay in hospital. Results: Among 14,264 patients infected with Omicron, the average length of hospital stay was six (4-8, Interquartile range) days. Fifty percent of the patients were discharged by the 6th day, and 90% were discharged by the 10th day. Patients of all ages are generally susceptible to COVID-19, and there was no difference in discharge time, but the average length of hospital stay of Tibetan patients with COVID-19 was longer than that of Han patients. According to the statistics of clinical symptoms, sore throat (38.7%) and fever (19.4%) were the most common symptoms, while muscle pain (17.4%), cough (16.6%), and expectoration (13.2%) were also common. In addition, patients with chronic gastritis had significantly longer hospital stays. Conclusion: Based on the experience of Tibet mobile cabin hospitals and data analysis, we believe that patients of all ages are generally susceptible to Omicron. Compared with other novel coronavirus strains, Omicron infected patients had a shorter hospital stay, and treatment of symptoms is expected to shorten the time of nucleic acid negative conversion.